User blog comment:Sefiros2211/Dante's Age/@comment-775152-20121207061630

First off, DmC is a reboot of the series; that means he is not the same Dante from previous games, even though they share the same name. Thus, this Dante is roughly equivalent to DMC3 Dante, just in a different story universe. DmC is a brand new origins story, borrowing concepts and characters from the original story but not impacting them at all. Think of it like New Spiderman vs. Old Spiderman: Old Spidey was bitten by a radioactive spider to gain his powers, while New Spidey was bitten by a genetically modified spider. Same basic outcome, same character name, different stories. Except in this case, New Spidey is DmC Dante while Old Spidey is Classic Dante.

Now to address the other, more fun part of your question:

We're never really given exact ages, though it's logical to assume that there are five to ten years between the events of the games: DMC3 puts Dante at roughly 18, based on his appearance and attitude; DMC1 has him at about 28, based on Trish's comment about how he lost his mother and brother to demons "20 years ago" and the fact that Dante was about 8 when his mother was killed; DMC4 would put him at about 36, if we assume Nero to be about 18 and if we assume that his father was a teenager at the time of his conception; DMC2 is the wildcard, though because he's finally calmed the buck down, it's assumed he's in his forties by that time.

As you can see, there are a lot of assumptions, and are endless ways to interpret any of the clues. For example; since Dante is a demon, he may not age exactly like a human, and might be much older than previously assumed. Also, I am of the personal (though by no way canon) belief that DMC2 Dante is actually an impostor, (read: Vergil,) and thus his age becomes a wildcard in that his adventure could happen at almost any time in the chronology.